Hollow polyester long fiber and preparation method therefor

ABSTRACT

A hollow polyester long fiber has a cross-sectional hollowness ranging from 20.0% to 45.0%, the long fiber in natural state being of a three-dimensionally crimped shape, and the radius of curvature of the crimped shape being 10.0 mm to 50.0 mm. The fluffy processed tows obtained by processing the hollow polyester long fiber have high fluffiness.

TECHNICAL FIELD

This disclosure relates to a hollow polyester long fiber of hollow crimped shape and a preparation method thereof, and the hollow long fiber is suitable for making long fiberfill.

BACKGROUND

In the textile industry, feathers and down of waterfowls such as goose down, duck down and the like, are usually filled in duvets, sleeping bags and various cold-proof and warmth retention products. Bird flu that has occurred worldwide has led to a sharp decline in the production of down, which has caused prices to rise. At the same time, consumers also have doubts about the safety of down. If the natural feathers are not adequately washed, it will cause bad odor. Therefore, it is necessary to remove the odor-causing dirt in advance and maintain the cleanliness of the feathers. Moreover, there are still problems in washing feather filling products such as feather bedding, feather jackets and the like.

To this end, the industry is committed to the use of synthetic fibers instead of animal down for filling. Chinese patent CN1861871A discloses a short-fiber type of down-like fiberfill, but the short-fiber fiberfill has low fluffiness, and a heat insulating material produced therefrom has a grainy feel when touched, while the short-fiber type down-like fiberfill is prone to shifting when washed. Therefore, there is an urgent need to develop a new type of filling material instead of down. Polyester fiber is easy to produce and has the advantage of low price. The development of polyester-based filling materials has a good market prospect.

It could therefore be helpful to provide a hollow polyester long fiber having a three-dimensionally crimped shape that is suitable for use in the production of long fiberfill, and a method of preparing the hollow polyester long fiber.

SUMMARY

Our hollow polyester long fiber has a cross-sectional hollowness ranging from 20.0% to 45.0%, and the hollow polyester long fiber has a three-dimensionally crimped shape in a natural state, and the crimped shape has a radius of curvature ranging from 10.0 mm to 50.0 mm.

The hollow polyester long fiber preferably has a monofilament fineness ranging from 4.0 dtex to 15.0 dtex, and more preferably from 5.0 dtex to 10.0 dtex.

The hollow polyester long fiber still has a three-dimensionally crimped shape after dry heat treatment at 160° C. for 3 minutes, and has a radius of curvature in a crimped state ranging from 3.5 mm to 10.0 mm.

The hollow polyester long fiber has a polymer raw material selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or a modified polymer thereof.

We also provide a method of preparing the above-mentioned hollow polyester long fiber, wherein a dried chip is melt-extruded by a screw and then conveyed to a metering pump through a pipe, the polymer accurately measured by the metering pump is conveyed to a spinning pack, a spinneret of the spinning pack is a hollow spinneret with a cooling distance ranging from 10 to 150 mm, and a wind speed of side blowing ranges from 25 to 90 m/min.

The cooling distance preferably ranges from 60 to 110 mm; and the wind speed of the side blowing ranges from 30 to 50 m/min.

The hollow polyester long fiber is obtained by a melt spinning process, has the advantages of simple production and low cost, and has a three-dimensional crimped structure, and is suitable for processing into a fluffy processed tow which can be used as long fiberfill.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a triangular hollow cross-sectional shape of a hollow polyester long fiber.

FIG. 2 is a view showing a quadrangular hollow cross-sectional shape of a hollow polyester long fiber.

FIG. 3 is a view showing a three-dimensionally crimped shape of a hollow polyester long fiber in a natural state.

FIG. 4 is a schematic view showing a measurement of a radius of curvature.

DETAILED DESCRIPTION

To develop a filler that can replace down, we provide a hollow polyester long fiber suitable for processing into a fluffy processed tow. Since the hollow fiber has a structural feature of three-dimensionally crimped shape, the obtained fluffy processed tow also has a three-dimensional structure so that the bulk of the fluffy tow is large, and a fluffy processed tow excellent in fluffiness can be obtained. In the fiber-forming polymers, the Young's modulus of the polyester fiber is relatively high so that the obtained fluffy processed tow has good pressure resistance and recovery.

The three-dimensionally crimped shape means that the fiber exhibits an irregular spiral structure in the long direction (FIG. 3) and, at the same time, due to the difference in alignment between a part of the monofilaments, the rotation mode and direction of the monofilaments are different to form a multi-dimensional stereoscopic form.

The hollow polyester long fiber is a hollow fiber produced by melt spinning technique. The molten polyester chips are discharged through a profiled hollow spinneret and then coiled after side blow cooling to obtain the hollow polyester long fiber. In the process of melt spinning, the hollow fiber is controlled to have a hollowness ranging from 20.0% to 45.0% and a radius of curvature of the three-dimensionally crimped shape ranging from 10.0 mm to 50.0 mm by adjusting the position of the side blowing to change the cooling distance, adjusting the wind speed of the side blowing, and the spinning speed. Compared to a solid fiber with the same fiber diameter, the fluffy processed filament obtained by using the hollow fiber has a higher fluffiness, and the higher the hollowness is, the more obvious the light weight is. If the radius of curvature of the hollow fiber is too small, the cohesion between the filaments of the fiber is high, the fiber is not easy to be split during the processing of the fluffy tow, and the diameter of the ring formed by the fiber is small, which affects the fluffiness of the processed tow. On the other hand, if the crimp radius of the fiber is too large, the diameter of the ring formed by the fiber after being processed into a fluffy processed tow is too large, which may weaken or fail to reflect the original three-dimensional effect of the sheath fiber, and also affect the fluffiness of the processed tow.

According to the differences in the shape and arrangement of the hollow spinneret discharge holes, and the change of the production process, the obtained hollow fiber has a slightly different cross section, and the hollow portion has a circular shape, an approximately triangular shape, an approximately square shape, an approximately pentagon shape and the like. At the same time, the number of holes in the hollow section is not limited to one hole.

The monofilament fineness of the hollow polyester long fibers is preferably in a range from 4.0 dtex to 15.0 dtex. As the raw material fiber for the fluffy processed tow, the higher the monofilament fineness of the fiber is, the better the rigidity of the fiber is, and meanwhile the better the fluffiness of the resulting fluffy tow is, and the better the pressure resistance and the recovery property are. However, if the diameter of the monofilament fiber is too large, it is not easy to be cooled during spinning, and the uniformity of the fiber is lowered, and the obtained fluffy tow has a hard hand feeling. Therefore, it is more preferable that the monofilament fineness of the hollow polyester long fiber is in a range from 5.0 dtex to 10.0 dtex.

The raw materials of the hollow polyester long fibers are mainly common polyesters such as polyethylene terephthalate, polytrimethylene terephthalate or polybutylene terephthalate. To impart a special function to the fluffy processed yarn, a modified copolymer of the above polymer such as an antibacterial and anti-mite modified polymer can also be used, and the same effect as the common polyester can be achieved in terms of fluffiness properties.

The hollow polyester long fiber is one of the raw materials for making fluffy processed tows for filling. The hollow polyester long fiber can be directly used as long fiberfill by directly combining N fibers into a fluffy processed tow, and can also be used in combination with other raw materials such as a fiber which is slightly lower in melting point to be made into a blended fiber, and then used as long fiberfill. Alternatively, the blended fiber and the hollow polyester long fiber are subjected to core-sheathing and then partially melted to obtain a more excellent fluffy processed tow, which is then used as long fiberfill.

The hollow polyester long fiber still has a three-dimensional shape after dry heat treatment at 160° C. for 3 minutes. The crimped shape changes due to the thermal shrinkage of the fiber, and the radius of curvature is preferably in a range from 3.5 mm to 10.0 mm. In this example, even after the subsequent processing, the hollow polyester long fiber can maintain a fluffy three-dimensionally crimped shape, and is excellent in hand feeling, fluffiness, heat retention and the like.

The long-fiber hollow polyester long fiber can be prepared by the following method, but is not limited to the method:

First, the raw material polyester chips are dried to reduce the water content of the polyester chips, improve the spinnability, and control the water content of the chips to be 50 ppm or less. The dried chips are spun by a general melt spinning method. The chips are melted by a screw or a hot plate and then conveyed to a metering pump through a pipe, and the melt polymer is accurately metered by the metering pump and then enters the spinning pack, wherein the spinneret used in the spinning pack is a spinneret dedicated to hollow fiber spinning. The polymer discharged from the spinneret is cooled, oiled and then coiled. To obtain a slightly crimped hollow fiber, the requirement for the cooling distance (the distance from the lower edge of the spinneret to the upper edge of the side-blowing for cooling) in the spinning process is relatively strict, and it is generally controlled within a range from 10 to 150 mm, preferably within a range from 60 to 100 mm. At the same time, to produce the difference between the structures on both sides of the hollow fiber, there is also limitation for the wind speed of the side blowing. According to the fiber type (total fineness and number of filaments), it is generally controlled within a range from 25 to 90 m/min, preferably from 30 to 50 m/min.

When the cooling distance is less than 10 mm, the polymer discharged from the spinneret is rapidly cooled, the asymmetric effect is obvious, the radius of curvature of the obtained fiber is too small, the cohesion between the fiber monofilaments is high, and the fluffing effect is affected, and at the same time the temperature of the spinneret is easily lowered to cause fiber breakage and thus the spinnability is not good. When the cooling distance is greater than 150 mm, the polymer discharged from the spinneret has been uniformly cooled to a certain extent. Even if forced cooling is then performed by the side blowing, the asymmetric effect is weakened, and the radius of curvature of the fiber is too large, which also affects the fluffing effect.

When the wind speed of the side blowing is less than 25 m/min, the asymmetric cooling effect is not obvious, and the radius of curvature of the fiber is too large. When the wind speed of the side blowing is greater than 90 m/min, the asymmetric effect is obvious, resulting in the curvature radius of the obtained fiber being too small, and excessive side blowing results in a large swing of the fiber, unstable spinning, and easy to appear floating monofilament and broken filament.

To prevent physical properties from differing between the filaments due to the difference in cooling, the arrangement of the spinneret discharge holes is preferably a “houndstooth” arrangement, which is often referred to as a diamond arrangement. Preferably, the spinning process mainly adopts a one-step spinning process, that is, spinning/stretching is completed simultaneously, that is, commonly known as FDY. However, it can also be obtained by a two-step process, that is, a pre-oriented fiber is first obtained, which is commonly known as POY, and then subjected to a drawing process by an extension machine, which is commonly known as DT.

The hollow polyester long fiber has a three-dimensional crimped structure and, at the same time, the fiber monofilament is relatively thick, and the fluffy processed tow obtained from the hollow long fiber has a high excluded volume, and has high fluffiness while having excellent compression resistance.

The test method is as follows:

(1) Test Method for Total Fineness and Monofilament Fineness

The total fineness test was performed according to the JIS L 1013:2010 standard, and the monofilament fineness was calculated by the total fineness and the number of filaments.

(2) Hollow Rate

The hollow long fiber was cut into thin slices (i.e., fiber cross section) in the cross-sectional direction, which were then photographed under a normal optical microscope to a suitable magnification, and the area S₁ of the hollow portion and the area S₂ of the entire fiber (including the hollow portion) were calculated according to the photograph, then it was calculated as:

Hollow ratio=(S ₁ /S ₂)×100%.

(3) Test Method for Radius of Curvature

Radius of curvature in a natural state: the yarn was passed through a scaler (for fineness measurement) to crimp the sample for 10 turns (1 m/turn), and then the sample to be tested was placed (suspended) for 8 hours or more in a constant temperature and humidity environment (20° C.×65% RH) to stabilize its state (FIG. 3), then the crimped part within 20 cm below the sample was selected to measure the radius, and 20 different places were selected for measurement and averaged, and the obtained data was the radius of curvature. The measuring instrument was a digital microscopy system (VHX-2000C) manufactured by KEYENCE. The magnification was 20 times, and the radius of curvature was measured by the calculation function of the radius of curvature in the software (FIG. 4). That is, the radius of curvature of the fibers was measured by three locations on the crimped fiber.

Curvature radius after dry heat treatment: the yarn was passed through a scaler (for fineness measurement) to crimp the sample for 10 turns, and then placed in a dryer for heat treatment. The treatment condition was 160° C.×3 min, and then the sample was placed in a constant temperature and humidity environment for 4 hours or more, and finally the crimped part within 20 cm of the lower portion was selected to measure the radius, and 20 different places were selected for measurement and averaged, and the obtained data was the radius of curvature.

(4) Fluffiness

Test according to the IDFB method:

(i) First, the sample to be tested was placed in an environment of 20° C.×65% RH for 8 hours or more so that the sample to be tested was stabilized; (ii) 30 g of sample were weighted, manually shaken to a fluffy state, placed in a measuring barrel and covered with a lid; (iii) the weight plate was moved down to the highest point of contact with the sample, then the weight plate was released to make it fall freely, and it was started to measure time at the time of releasing the weight plate, and after 1 minute for stabilization, the height was read and recorded; (iv) the lid was opened to take out the sample, which was shaken again to the fluffy state, placed in the measuring barrel and covered with the lid, and measured again according to step (iii), and the same method was repeatedly tested for 5 times; (v) the fluffiness was calculated by calculating the average height of the 5 times of tests.

The contents are explained below by way of examples, but this disclosure is not limited to the contents listed in the examples.

Example 1

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 25 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 300T-20f, a triangular hollow cross section, a hollowness of 20.0%, a monofilament fineness of 15.0 dtex, and a radius of curvature of 50.0 mm before heat treatment, and a radius of curvature of 10.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 390 inch³/30 gas shown in Table 1.

Example 2

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 40 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 150T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 15.0 dtex, and a radius of curvature of 42.0 mm before heat treatment, and a radius of curvature of 8.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 600 inch³/30 gas shown in Table 1.

Example 3

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 40 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 60T-4f, a triangular hollow cross section, a hollowness of 45.0%, a monofilament fineness of 15.0 dtex, and a radius of curvature of 37.0 mm before heat treatment, and a radius of curvature of 7.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 800 inch³/30 g as shown in Table 1.

Example 4

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 40.0 mm before heat treatment, and a radius of curvature of 7.8 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 650 inch³/30 gas shown in Table 1.

Example 5

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 50 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-20f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 5.0 dtex, and a radius of curvature of 35.0 mm before heat treatment, and a radius of curvature of 6.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 610 inch³/30 g as shown in Table 1.

Example 6

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 75 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 60T-15f, a triangular hollow cross section, a hollowness of 45.0%, a monofilament fineness of 4.0 dtex, and a radius of curvature of 10.0 mm before heat treatment, and a radius of curvature of 3.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 480 inch³/30 g as shown in Table 1.

Example 7

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 70 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 65T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 6.5 dtex, and a radius of curvature of 30.0 mm before heat treatment, and a radius of curvature of 6.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 580 inch³/30 g as shown in Table 1.

Example 8

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 70 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 50T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 5.0 dtex, and a radius of curvature of 20.0 mm before heat treatment, and a radius of curvature of 4.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 520 inch³/30 g as shown in Table 1.

Example 9

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 25 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 60T-4f, a quadrangular hollow cross section, a hollowness of 45.0%, a monofilament fineness of 15.0 dtex, and a radius of curvature of 42.0 mm before heat treatment, and a radius of curvature of 8.1 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 760 inch³/30 gas shown in Table 1.

Example 10

As a raw material, conventional polytrimethylene terephthalate chips (i.e., common 3GT) were used, and the polytrimethylene terephthalate was dried by a pre-crystallization dehumidifying dryer to have a water content of 30 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 38.0 mm before heat treatment, and a radius of curvature of 7.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 630 inch³/30 gas shown in Table 1.

Example 11

As a raw material, conventional polybutylene terephthalate chips (i.e., common PBT) were used, and the polybutylene terephthalate was dried by a pre-crystallization dehumidifying dryer to have a water content of 33 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 36.0 mm before heat treatment, and a radius of curvature of 7.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 600 inch³/30 g as shown in Table 2.

Example 12

As a raw material, cationic modified polyethylene terephthalate chips were used, and the cationic modified polyethylene terephthalate was dried by a pre-crystallization dehumidifying dryer to have a water content of 30 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 33.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 33.0 mm before heat treatment, and a radius of curvature of 6.4 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 610 inch³/30 g as shown in Table 2.

Example 13

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 10 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 40.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 12.0 mm before heat treatment, and a radius of curvature of 3.6 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 490 inch³/30 g as shown in Table 2.

Example 14

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 60 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 37.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 30.0 mm before heat treatment, and a radius of curvature of 6.1 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 600 inch³/30 g as shown in Table 2.

Example 15

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 90 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 32.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 34.0 mm before heat treatment, and a radius of curvature of 9.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 720 inch³/30 g as shown in Table 2.

Example 16

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 110 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 30.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 38.0 mm before heat treatment, and a radius of curvature of 12.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 620 inch³/30 g as shown in Table 2.

Example 17

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 150 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 25.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 44.0 mm before heat treatment, and a radius of curvature of 14.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 550 inch³/30 g as shown in Table 2.

Example 18

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 90 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 35.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 18.0 mm before heat treatment, and a radius of curvature of 3.9 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 510 inch³/30 gas shown in Table 2.

Example 19

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 50 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 28.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 28.0 mm before heat treatment, and a radius of curvature of 4.5 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 530 inch³/30 g as shown in Table 2.

Comparative Example 1

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a common round hole spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 25 m/min, and the polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the fiber were as follows: a fiber type of 56T-24f, a solid circular cross section, a monofilament fineness of 2.3 dtex, and no crimping property before and after heat treatment. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 240 inch³/30 g as shown in Table 3.

Since the cross section of the fiber was solid, the obtained fiber did not have curl, had a small fluffiness, and was not suitable for use as fiberfill instead of feather.

Comparative Example 2

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 90 mm. The wind speed of the side blowing was 35 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 10.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 40.0 mm before heat treatment, and a radius of curvature of 10.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 310 inch³/30 g as shown in Table 3.

Since the hollowness of the fiber was too small, although it had a radius of curvature, it was not light in weight and had a small fluffiness, and was not suitable for use as fiberfill instead of feather.

Comparative Example 3

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 5 mm. The wind speed of the side blowing was 35 m/min, and spinning was performed through the DSD high-speed spinning process. Since the cooling distance was too short, although the spinning could be performed, the phenomenon of broken filaments and floating filaments was serious, and the feasibility of production was low as shown in Table 3.

Comparative Example 4

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 110 m/min, and spinning was performed through the DSD high-speed spinning process. Since the wind speed of the side blowing was too fast, although the spinning could be performed, serious fiber vibration led to serious broken filaments and floating filaments, and the feasibility of production was low as shown in Table 3.

Comparative Example 5

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 200 mm. The wind speed of the side blowing was 70 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 15.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 65.0 mm before heat treatment, and a radius of curvature of 23.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 350 inch³/30 g as shown in Table 3.

Since the cooling distance was too large, the radius of curvature of the obtained fiber was too large to reflect the three-dimensional effect of the fiber, resulting in small fluffiness.

Comparative Example 6

As a raw material, semi-dull polyester chips (T200N manufactured by Toray Fibers (Nantong) Co., Ltd.) were used, and the polyester chips were dried by a pre-crystallization dehumidifying dryer to have a water content of 39 ppm after drying. The dried chips were melted and extruded by a screw and conveyed to a metering pump through a pipe. The polymer accurately metered by the metering pump was conveyed to the spinning pack. The spinneret of the spinning pack was a hollow special spinneret with a cooling distance of 65 mm. The wind speed of the side blowing was 20 m/min, and the hollow polyester fiber was obtained through the DSD high-speed spinning process. The characteristics of the hollow fiber were as follows: a fiber type of 100T-10f, a triangular hollow cross section, a hollowness of 12.0%, a monofilament fineness of 10.0 dtex, and a radius of curvature of 55.0 mm before heat treatment, and a radius of curvature of 20.0 mm after dry heat treatment at 160° C. for 3 minutes. The fiber was selected as the raw material for the sheath fiber and the core fiber and was fed by overfeeding at a ratio of sheath filament feeding speed/core filament feeding speed of 20 times, processed into core-sheath type fluffy filaments, and every 6 filaments were combined into one to obtain a fluffy processed tow, and the fluffiness of the fluffy processed tow was tested to be 350 inch³/30 g as shown in Table 3.

Since the wind speed of the side blowing was too small, the radius of curvature of the obtained fiber was too large to reflect the three-dimensional effect of the fiber, resulting in small fluffiness.

TABLE 1 Example Example Example Example Example Example Example Example Example Example Item 1 2 3 4 5 6 7 8 9 10 Main Polymer Common Common Common Common Common Common Common Common Common Common process of PET PET PET PET PET PET PET PET PET 3GT spinning Spinneret form Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Cooling distance 65 65 65 65 65 65 65 65 65 65 (mm) wind speed of 25 40 40 35 50 75 70 70 25 35 side blowing (m/min) Fiber Cross section Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow properties form Shape of hollow Triangular Triangular Triangular Triangular Triangular Triangular Triangular Triangular Quad- Triangular part rangular Fiber variety 300T-20f 150T-10f 60T-4f 100T-10f 100-20f 60T-15f 65T-10f 50T-10f 60T-4f 100T-10f Hollowness (%) 20.0 30.0 45.0 30.0 30.0 45.0 30.0 30.0 45.0 30.0 Monofilament 15.0 15.0 15.0 10.0 5.0 4.0 6.5 5.0 15.0 10.0 fineness (dtex) Radius of 50.0 42.0 37.0 40.0 35.0 10.0 30.0 20.0 42.0 38.0 curvature (mm) Radius of 10.0 8.5 7.0 7.8 6.5 3.5 6.0 4.5 8.1 7.5 curvature after heat treatment (mm) Fluffiness of fluffy processed 390 600 800 650 610 480 580 520 760 630 tow (inch³/30 g)

TABLE 2 Example Example Example Example Example Example Example Example Example Item 11 12 13 14 15 16 17 18 19 Main Polymer Common Cationic Common Common Common Common Common Common Common process of PBT PET PET PET PET PET PET PET PET spinning Spinneret form Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Cooling distance 65 65 10 60 90 110 150 65 65 (mm) wind speed of 35 35 35 35 35 35 35 90 50 side blowing (m/min) Fiber Cross section Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow Hollow properties form Shape of hollow Triangular Triangular Triangular Triangular Triangular Triangular Triangular Triangular Triangular part Fiber variety 100T-10f 100T-10f 100T-10f 100T-10f 100T-10f 100T-10f 100T-10f 100T-10f 100T-10f Hollowness (%) 30.0 33.0 40.0 37.0 32.0 30.0 25.0 35.0 28.0 Monofilament 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 fineness (dtex) Radius of 36.0 33.0 12.0 30.0 34.0 38.0 44.0 18.0 28.0 curvature (mm) Radius of 7.0 6.4 3.6 6.1 9.5 12.5 14.5 3.9 4.5 curvature after heat treatment (mm) Fluffiness of fluffy processed 600 610 490 600 720 620 550 510 530 tow (inch³/30 g)

TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Item example 1 example 2 example 3 example 4 example 5 example 6 Main Polymer Common Common Common Common Common Common process of PET PET PET PET PET PET spinning Spinneret form Circular Hollow Hollow Hollow Hollow Hollow Cooling distance 65 90 5 65 200 65 (mm) wind speed of 25 35 35 110 70 20 side blowing (m/min) Fiber Cross section Solid Hollow — — Hollow Hollow properties form Shape of hollow — Triangular Triangular Triangular part Fiber variety 56T-24f 100-10f 100T-10f 100T-10f Hollowness (%) — 10.0 15.0 12.0 Monofilament 2.3 10.0 10.0 10.0 fineness (dtex) Radius of — 40.0 65.0 55.0 curvature (mm) Radius of — 10.0 23.0 20.0 curvature after heat treatment (mm) Fluffiness of fluffy processed 240 310 350 350 tow (inch³/30 g) 

1.-8. (canceled)
 9. A hollow polyester long fiber having a cross-sectional hollowness of 20.0% to 45.0%, and the long fiber has a three-dimensionally crimped shape in a natural state, and the crimped shape has a radius of curvature of 10.0 mm to 50.0 min.
 10. The hollow polyester long fiber according to claim 9, wherein the long fiber has a monofilament fineness of 4.0 dtex to 15.0 dtex.
 11. The hollow polyester long fiber according to claim 10, wherein the long fiber has a monofilament fineness of 5.0 dtex to 10.0 dtex.
 12. The hollow polyester long fiber according to claim 9, wherein the long fiber has a radius of curvature of 3.5 mm to 10.0 mm after dry heat treatment at 160° C. for 3 minutes.
 13. The hollow polyester long fiber according to claim 9, wherein the polyester is selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or a modified polymer thereof.
 14. A method of preparing the hollow polyester long fiber according to claim 9, wherein a dried chip is melt-extruded by a screw and then conveyed to a metering pump through a pipe, the polymer accurately measured by the metering pump is conveyed to a spinning pack, a spinneret of the spinning pack is a hollow spinneret with a cooling distance of 10 to 150 mm, and a wind speed of side blowing of 25 to 90 m/min.
 15. The method according to claim 14, wherein the cooling distance is 60 to 110 mm.
 16. The method according to claim 14, wherein the wind speed of the side blowing is 30 to 50 m/min.
 17. The hollow polyester long fiber according to claim 10, wherein the long fiber has a radius of curvature of 3.5 mm to 10.0 mm after dry heat treatment at 160° C. for 3 minutes.
 18. The hollow polyester long fiber according to claim 10, wherein the polyester is selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or a modified polymer thereof.
 19. The method according to claim 15, wherein the wind speed of the side blowing is 30 to 50 m/min. 